1. Field of the Invention
The field of the invention is hand held electric appliances and more particularly electric toothbrushes.
2. Description of Related Art
The benefits of electric toothbrushes are well known. One type of electric toothbrush utilizes an eccentrically moving weight coupling to motor's rotating shaft to cause a handle of the toothbrush to vibrate, the vibration of the handle being transmitted to the bristles of the brush via a neck coupling the bristle portion/head of the brush to the handle. The use of such devices is not always desirable however, at least in part because of the relatively large amount of vibration required in the handle in order to get an acceptable amount of vibration of the bristles, and the corresponding high energy usage and the uncomfortable degree of vibration transferred to the hand of a person using such a brush. Examples of such prior art toothbrushes can be found in U.S. Pat. Nos. 3,685,080, 5,421,726, 5,651,157, 5,706,542, 5,718,667, and 5,706,542. An eccentric weight, as the term is used herein, is a weight whose center of mass is not on the center of rotation of the weight.
Unfortunately, current toothbrushes are constructed in a manner that is cost prohibited. Moreover, such toothbrushes are unduly cumbersome because of their weight, and size, and/or because of a battery charger accessory. Thus, there is a continuing need for affordable electric toothbrushes that are not unduly cumbersome, are relatively inexpensive and do not use excessive energy.
The following art defines the present state of this field:
Giuliani et al., U.S. Pat. No. 5,189,751 describes a vibrating toothbrush, which includes a toothbrush body and a lever arm having toothbrush bristles at one end thereof. The lever arm is mounted for pivotal movement at a pivot member, which is in the vicinity of the other end of the lever arm. In one embodiment, a pair of permanent magnets are provided at the other end of the lever arm, positioned side-by-side with opposite polarities. An electromagnet is provided to the rear of the lever arm. The electromagnet includes an E-core having top, bottom and center legs with a coil wound around its center leg which receives an alternating current driving signal from an oscillator/battery section. The frequency of operation is in the range of 150-400 Hz. The action of the alternating current in the electromagnet causes the lever arm to move about the pivot member, first in one direction and then in an opposing direction to provide the desired vibrating effect.
Hahn, et al., U.S. Pat. No. 5,987,681 describes an electric toothbrush with a handle, a brush head and a shank, which connects the handle to the brush head. A rotary motor is arranged in the handle and drives an unbalanced mass. The unbalanced mass driven by the motor is supported on one side or on both sides in the shank close to the brush head and is driven via an extended drive shaft, preferably an intermediate shaft, by the motor.
McDougall, U.S. Pat. No. 6,421,866 describes an electric toothbrush having a balanced mass provided on a shaft extension that rotates freely about a longitudinal axis, inside a cavity in a brush head. The shaft extension and the brush head are flexibly coupled to a drive shaft and to a remote end of a shank respectively. When the shaft is rotated by an electric motor in a handle, of the toothbrush, an offset stub axle, effectively at a remote end of the shaft extension and fitted to a bearing in the brush head, causes the brush head to vibrate. The shank is not caused to vibrate to any extent.
Wolf, Susan, Hendrix, Ph.D., Suzanne (1998). Automated Toothbrush Comparison Statistical Report. Clinical Research Associates, describes an evaluation of 6 toothbrushes that was performed using two populations to determine if toothbrushes with sonic or ultrasonic capabilities reduce dental plaque, more effectively than a manual or other automated toothbrushes. The Sensonic (Teledyne) and Sonicare (Optiva) toothbrushes claim sonic capabilities and the Ultrasonex (Sonex) claims ultrasonic capabilities. Control toothbrushes were the Interplak (Corsair) and Ultra Plaque Remover (Braun), which are automated toothbrushes not claiming sonic or ultrasonic capabilities, and the Advantage (Oral-B) manual toothbrush. Population one consisted of 24 non-handicapped subjects, while Population two consisted of 24 institutionalized handicapped subjects. Non-handicapped subjects were included to represent the majority of the population, while handicapped subjects were included because they have been reported as having frequent problems with heavy plaque in their oral cavities due to lack of manual dexterity necessary for effective tooth brushing.
Staff. (1998, July). CRA Status Report: Toothbrushes, Sonic & Ultrasonic. CRA Newsletter. P. 2-3, provides a comparison between sonic, ultrasonic, and manual toothbrushes. CRA laboratory & clinical studies compared plaque removal capability, test subject preferences, durability, & maintenance of 6 different toothbrushes over a 1¼ year period.
The prior art teaches vibrating toothbrushes, rotary bristle toothbrushes, and laterally oscillating toothbrushes. The prior art also includes electric toothbrushes in common use such as the Advantage by Oral-B, Interplak by Conair, Sensoic by Teledyne, Sonicare by Optiva, Ultra PR by Braun and Ultrasonex by Sonex. However, the prior art does not teach the matching of the natural frequency of vibration of the toothbrush itself with the purposely generated vibration frequency of the operational engine of the toothbrush. The present invention fulfills these needs so as to enable low energy usage, low energy loss in the handle of the device, improved vibratory action in the bristles and other benefits, and provides further related advantages as described in the following summary.